A girls’ track coach in Montgomery County faces sex offense and assault charges after having sex with a 14-year-old girl he met through social media, officials said Wednesday.

Onaje Robinson, 42, allegedly struck the girl with a wooden stick during the Aug. 20 encounter at his apartment in Germantown, which the girl described as nonconsensual, according to a police charging document filed in court. Robinson turned himself in to detectives Tuesday night, was booked at the Montgomery jail and released on a $10,000 bond, according to court records.

In a statement to police, Robinson said that the sex was consensual and that the girl told him she was 20, according to court records. Robinson could not be reached to comment. Court records do not indicate whether he has an attorney.

The victim in the police case lives in Anne Arundel County and is not a Montgomery student.

Montgomery school officials said that last week — after learning of the police investigation — they put Robinson on unpaid administrative leave.

Onaje Robinson (Montgomery County Police)

He had started as a volunteer assistant track coach in 2013 for the girls’ team at Seneca Valley High School, in Germantown, school officials said. The next year, he was hired on a coaching contract, which was renewed through last spring. Robinson had not signed a new contract for this school year, but track season had not started, school officials said.

“The actions alleged in the charging document are troubling and unacceptable,” the school’s principal, Marc J. Cohen, said in a letter sent to parents. “This behavior is not a reflection of the values of Seneca Valley High School.”

According to the charging document, on the afternoon of Aug. 20, a woman in Anne Arundel called police to her home. She said she had learned earlier that day — in the early morning hours — that her daughter had left the house and had sex with an older man, court files state. The girl spoke with police. She said that about a week earlier, she had met a man “she came to know as ‘Jay’ on social media,” according to court records.

The girl told police that she told Jay she was 14, according to court records, and that the two eventually agreed to meet in person. That happened about 1 a.m. Aug. 20, when Jay parked near her home, picked her up and drove her to his apartment, 45 minutes away, in Germantown, police allege.

“The victim stated that they [lay] on the bed and that they watched a Netflix movie,” police wrote in the charging document.

That led to a sexual encounter and to Robinson allegedly hitting her with the stick, the girl told police. She also gave them the man’s cellphone number, which led them to Robinson.

During questioning by detectives, he said he met the alleged victim over social media, picked her up at her home, took her to his apartment and struck her with the stick during a sexual encounter, according to court records.

But Robinson said that the sex was consensual, the court records state, and that the girl had represented herself as being 20 on social media.

“It is worth noting,” police wrote in court papers, “that the suspect stated that when he picked up the victim and saw her in person for the first time, he thought she looked young.”